3. What do the different phases bring together?

3.1 Phase 1

A scenario consists of at least two elements:

• an initiating event ;

• a consequence.

In addition to the two elements defined above, a scenario can include :

• realization conditions, which correspond to the conditions necessary for the initiating event to lead to the envisaged consequence;

• failure of the safety barriers in place to cope with the accident scenario.

The scenarios to be studied may be the result of a preliminary analysis phase such as HAZOP. In this case, the scenarios are those identified by the working group as requiring further...